Liquid rosin sizes containing anti-stratifying and viscosity decreasing agent



United States LIQUID ROSIN SIZES CGNTAINING ANTI-STRATI- FYING AND VISCQSETY DECREASING AGENT No Drawing. Application February 25, 1954 Serial N 0. 412,644

Claims. (Cl. 106-238) The present invention relates to rosin sizes. More particularly, the present invention relates to liquid rosin sizes containing a small but effective amount of an alkali metal acetate as agent decreasing the viscosity of these sizes or such larger amount as both decreases the viscosity of the sizes and substantially prevents Stratification of the sizes on storage.

Rosin sizes have their principal use in the manufacture of paper. These sizes are manufactured on a large commercial scale by heating a natural or modified rosin above its melting point, forming a hot caustic solution from water and an alkali metal alkali such as potassium or, more commonly, sodium hydroxide or carbonate, and reacting the alkali solution with the rosin. The rosins referred to are organic acids. Neutralization of these acids by the caustic takes place within a few hours, the product being a viscous soap dispersion. In this process, the amount of water employed is controlled so that the size contains between about 50% and 80%85% of solids, on the one hand to avoid sizes as dilute that they cannot be shipped economically, and on the other hand to avoid sizes so concentrated and, therefore, viscous that they cannot be pumped.

The amount of alkali employed in this manufacture is at least about 60% of that required for complete neutralization so that the size contains about 40% of free rosin acids, a lower amount of alkali yielding a size which contains so much free rosin acids that it cannot be successfully diluted for application to paper. On the other hand, the amount of alkali maybe sutlicient to completely neutralize the rosin, and this yields satisfactory sizes.

In commercial practice, liquid rosin sizes generally contain between 60% and 80% of solids by weight, thus minimizing shipping costs while providing a product havr ing a pumpable viscosity at a tem erature of about 60- 70 C., this being the standard temperature at which sizes are handled within paper mills. Moreover, sufficient alkali is used to cause at least 65 %-75% neutralization of the rosin, this amount insuring that the resin possesses excellent dilutability in water while maintaining consumption of alkali and the viscosity of the product at minimum practical values.

Frequently, liquid rosin sizes are stored by the manufacturer before they are shipped in tank cars, and these sizes are further stored by paper manufacturers before use. It is known that during these. periods of storage liquid rosin sizes of the commercially practicable types mentioned, that is, sizes containing from about 5% to 25% of free rosin acids and about 60% to 80% of solids, stratify on storage and separate into two layers. The bottom layer is more viscous than the upper layer. Hence, when a liquid rosin size has been prepared of maximum pumpable viscosity, allowance being made for the increase in viscosity which normally takes place on aging, storage of the size results in separation of-a bottom layer which is beyond the range of normal pumpability atent otherwise possess.

and which, therefore, can be removed from the storage tank only with difficulty.

A further disadvantage is that the upper layer is usually darker in color than the lower layer, and this introduces a problem of color control in the manufacture of paper.

Stratification of liquid rosin size often becomes evident in the laboratory in 35 hours and, in the case of resin stored in large commercial tanks, in about 3 days The phenomenon is not spontaneously reversible and homogeneity can be restored only by thorough mixing of the contents of the tank.

The discovery has now been made that liquid rosin sizes of the composition mentioned are much improved in terms of decreased viscosity by a dissolved content of between about /2% and about 6% of sodium acetate, based on the solids content of the size, that from about /2% to about 3% of sodium acetate inhibits stratifica tion, and that stratiiioation is substantially completely prevented by the presence therein of between about 3% and 6% by weight of dissolved sodium acetate, also based on the weight of solids in the size. It has further een found that separation of the sizes into phases takes place when more than about 6%-8% of sodium acetate is present, the sodium acetate in this instanceacting to salt out the rosin soap resulting also in an actual increase in viscosity.

From the foregoing it will be seen that the subject matter of the present invention broadly comprises aliquid rosin size of about'5% to 25% free rosin acids content containing about 60% to 30% solids by weight, said size being impr ved by the presence of an effective amount between about /2% and'6% based on-th'e weight of the solids, of sodium acetate dissolved therein as agent decreasing tie viscosity of the size.

The amount of sodium acetate which should be present within the range mentioned to prevent Stratification varies With the type of rosin employed, the solids content of the size, the amount offree rosin acids in the size, and the temperature of the size. As a result, the n'iinirnnm eiiective amount can best be determined in each instance by laboratory trial. in general, with regard to liquid rosin sizes of the composition mentioned',we have, found that fortified rosin sizes'of low solids content but containing an intermediate amount of free rosin acids show the greatest and most rapid stratification, and that with regard to these sizes, higher temperatures favor stratification. For example, a fortified rosin size con-- taining 60% or 70% solids and 15% of free rosin acids is particularly prone to stratify and requires somewhat more of the acetate salt for sta'biliz'ation'at the upper normal storage temperature of C. th-an'does ordinary rosin size containing 80% solids andl5% free rosin acids at the lower normal storage temperature of 50 C.

Sodium acetate is fully suitable for use according to the resent invention, and no reason is known why potassium acetate should not also be'eifective. The latter is therefore included within the broad scope of the present in vention.

It is a particular feature ofthe present invention that the presence of only a small amount of sodium acetate very -greatly decreases the. .viscosityof the sizes often to only a small fraction of the values which they would I Since the viscosity of liquid rosin sizes increases as their temperature falls, and since rosin sizes are normally stored in heated storage tanks, this means that rosin in such tanks can be stored at lower temperatures than would otherwise be the case, while still preserving the size at pumpable viscosity. It is the customary practice of paper mills to store rosin size in tanks maintained at a temperature between about 60-70 C. The presence of sodium acetate permits the same sizes to be stored at a temperature about C. lower without increase in viscosity, thus permitting substantial economy in the heat supplied.

It is a further advantage that the sodium acetate does not in any way alter the color of the size or affect the usefulness of the size in the manufacture of paper.

Freshly prepared liquid rosin size, when stored at normal temperatures within the range of 50-80 C. in creases rapidly in viscosity during the course of about the first seven days, the viscosity at that time often being several times that of the initial viscosity of the material. Thereafter the viscosity of the size generally remains at or near the high value reached towards the end of the first week of storage. It is a further most important advantage that the action of sodium acetate is a permanent one, the stabilized sizes of the present invention having a much lower viscosity during and after this period than corresponding sizes containing no sodium acetate.

In the manufacture of the liquid rosin sizes to which the present invention is directed, numerous forms of rosin are currently employed and include gum rosin, wood rosin, and tall oil rosin, the latter being a new development in the rosin field for which standards have been promultermed fortified rosins and fortified rosin sizes are disclosed broadly in U. S. Patent Nos. 2,628,918 and 2,385,794.

It will be understood that liquid rosin sizes, in addition to the foregoing, commonly contain a number of was added an equal volume of deionized water.

and decreasing the viscosity of a liquid fortified rosin size is illustrated as follows.

A liquid fortified rosin size was prepared by heating 15,000 pounds of M grade gum rosin to 150 C. and slowly adding 600 pounds of maleic anhydride. Reaction of the maleic anhydride was complete in 3 hours at about l70-l80 C., the product being fortified rosin containing the Diels-Alder rosin maleic anhydride product.

In a separate vessel 1,720 pounds of sodium hydroxide was dissolved in 23,700 pounds of water and the mixture heated to 95 C. The molten fortified rosin and the hot caustic solution were separately but simultaneously pumped into a cook tank and the mixture agitated by agitation of live steam from the bottom. Reaction of the caustic was complete in 2 hours. The resulting size had a free rosin acids content of 19% and a solids content of 70%. I

Two samples, about a quart in size, were withdrawn. To one (Sample A) was added sufiicient of an approximately saturated hot aqueous sodium acetate solution to provide 1.4% of sodium acetate based on the weight of the solids therein. To the second (the control sample) Both samples were stored at 80 C. and observed at the end of this time for Stratification. The viscosity of the samples was determined initially and after 8 days, in both cases after thorough stirring to make the samples homogeneous and adjustment of the sizes to the temperatures shown. Stratification was deemed to take place when two distinct layers could be observed. The samples were rated on an arbitrary scale on which 4 indicates bad stratification, 1 indicates acceptably slight stratification, and 0 indicates no noticea'ole stratification. Results are as follows:

other materials. Included are the lower aliphatic alcohols and rosin esters therewith since rosin size may be 715mm nag Viscosit flat prepared from the latter. Moreover, natural rosins con- Percent 0 5 it m.

tam small amounts of unsapomfiable materials mcludp e igg (1 :5 .31:

ing lignin and sterols. Sizes containing these materials 8mm y undergo stratificanon on storage and the SOdlllIIl acetate 49 is advantageously p y fi Control Nil"... 3,432 0,510 758 1,137 4 The sodium acetate may be introduced at any desirable A L4 2 3, 718 711 711 2 point in the manufacture of the rosin size. For example,

it may be dispersed into the molten rosin itself or may ggii g gg 3011mm of sizebe dissolved in the liquid size subsequent to its preparation. Since, however, liquid rosin size is normally produced on a very large industrial scale it has been found most convenient to dissolve the sodium acetate in the water in which the alkali metal alkali is dissolved. In this manner uniform distribution of the antistratification agent is most readily efiected, and separate metering of the agent becomes unnecessary.

In the present specification, the term percent free rosin acids is used to designate the proportion of the rosin acids, as found by titration, which are not neutralized by the alkali-metal alkali during manufacture of the size.

The invention will be more particularly described with reference to the examples which follow, which are intended only to illustrate specific embodiments of the invention and which are not to be construed as limitations thereon.

,tain 1.4% of sodium acetate.

Example 2 The eifect of sodium acetate in preventing stratification of rosin size, together with its effect on the viscosity of the size, is illustrated by the following.

A fortified rosin size containing 70% solids and 11% free rosin acids was made by the method of Example 1, the amount of sodium hydroxide being increased to 1,880 pounds, and control and sodium acetate-containing sam- Example I ples were prepared and tested also as described in Ex- The efiect of sodium acetate in inhibiting stratification ample 1. Results are as follows:

Percent Viscosity (on) at 65 0. Viscosity (ep.) at 71 0. Sample Sodium Acetate Start 4Days SDays 12 Days Start 4Days 8Days 12 Days 1 Based on solids content or size.

1 Too viscous to stratify.

In this case the peak viscosity of the sodium acetatecontaining size was much lower than the initial viscosity of the control sample. From previous experience it is known that the viscosity of Sample B over the period tested was lower than the viscosity of Sample A, and that a somewhat lower amount of sodium acetate would also have prevented stratification.

We claim:

1. A liquid rosin size of from about 5% to 25% free rosin acids content containing between about 60% to 80% of solids by weight, said size containing an effective amount between about /Q% and 6%, based on the weight of said solids, of dissolved sodium acetate as agent decreasing the viscosity of said size.

2. A liquid rosin size according to claim 1 containing a rosin-maleic anhydride adduct.

3. A liquid rosin size of from about 5% to 25% free rosin acids content containing between about and 80% of solids by weight, said size being inhibited against Stratification on storage by the presence of an effective amount between about 3% and 6% based on the weight of said solids, of sodium acetate dissolved therein.

4. A liquid rosin size of about 15% free rosin acids content containing about of solids by weight, said size containing an effective amount between about 16% and 6%, based on the weight of said solids, of dissolved sodium acetate as agent decreasing the viscosity of said size. 7

5. A liquid rosin size according to claim 4 containing a rosin-maleic anhydride adduct.

References Cited in the file of this patent UNITED STATES PATENTS 2,027,166 Harding et a1. Jan. 7, 1936 2,186,014 Ellis Jan. 9, 1940 2,192,488 Reilly Mar. 5, 1940 2,213,943 Auer Sept. 10, 1940 FOREIGN PATENTS 651,302 Great Britain May 14, 1951 

1. A LIQUID ROSIN SIZE OF FROM ABOUT 5% TO 25% FREE ROSIN ACIDS CONTENT CONTAINING BETWEEN ABOUT 60% TO 80% OF SOLIDS BY WEIGHT ABOUT 1/2% AND 6%, BASED ON THE TIVE AMOUNT BETWEEN ABOUT 1/2% AND 6%, BASED ON THE WEIGHT OF SAID SOLIDS, OF DISSOLVED SODIUM ACETATE AS AGENT DECREASING THE VISCOSITY OF SAID SIZE. 